1. Field of the Invention
The present invention relates to an information recording apparatus and a data writing control device therefor, and, in particular, to an information recording apparatus employing recording media including a plurality of recording surfaces integrally combined, and a plurality of sets of reading heads and writing heads provided therefor, as well as a data writing control device therefor.
2. Description of the Related Art
As a typical example of such a information recording apparatus employing recording media including a plurality of recording surfaces integrally combined, and a plurality of sets of reading heads and writing heads provided therefor, a hard disk drive (HDD) is known which is used heavily as a storage in a personal computer or such.
Along with a recent demand for an increase of a recording speed and also of a recording density of the hard disk drive, it is desired to further increase the number of information recording tracks per unit width regarded as the information recording density of a disk-shaped recording medium, i.e., a so-called TPI (track per inch). In order to increase the TPI, it is necessary to increase an accuracy of positioning of a relevant writing head at a desired track, i.e., an on-track accuracy. In order to increase the on-track accuracy, it is required to increase a servo sampling frequency for obtaining a positioning signal provided for appropriately positioning the read/write heads. In order to increase the servo sampling frequency for the purpose of achieving high-speed and high-density information recording, it is necessary to shorten intervals at which servo information is previously provided on the disk-shaped recording medium.
According to a so-called data-surface-servo method which is applied recently as a data writing positioning method of a hard disk drive, the above-mentioned servo information provided for positioning the writing head is not provided in a certain special zone, but is provided in a zone of the recording surface which is originally provided for writing user data, in a mixed manner. Accordingly, the shortening of the intervals of the servo information provided on the disk-shaped recording medium for the purpose of increasing the servo sampling frequency to achieve high-speed and high-density information recording, may result in a substantial reduction of the user data recording capacity at the same time accordingly. As a result, the substantial data recording density may degrade, and thus, the data format efficiency may degrade.
Further, an apparatus in which the hard disk drive is installed may be a carriable or a mobile apparatus such as a notebook personal computer, a cellular phone, or such. As a result, a performance is required for the hard disk drive in which, even an external vibration or an impact is applied to the device, a normal operation can be kept uninterrupted. For this purpose, the above-mentioned servo sampling frequency may be further increased, or, a shock sensor or such may be provided, and an information writing operation may be forcibly interrupted when an external impact more than a certain level is detected, for at least avoiding an erroneous recording which otherwise occurs due to occurrence of a so-called off-track phenomenon in which the writing head deviates from a relevant track during information writing operation. However, according to the latter method, an actual control to interrupt the information writing operation is very difficult. In fact, according to a delicate adjustment variation, the writing operation may be forcibly interrupted even when the impact actually applied is not so large as to actually cause the off-track phenomenon. In such a case, the data recording performance may degrade. On the other hand, the off-track phenomenon actually may occur even by a light impact, and, in such a case, an erroneous recording operation occurs without an interruption of the information writing operation, whereby data on a neighbor track may be erroneously overwritten and thus erased, or such.